The present invention relates to improvements in the field of anesthesia. More particularly, the invention is concerned with a single breath induction anesthesia apparatus.
When it is necessary to anesthetise a patient, it is highly desirable to pre-oxygenate the patient prior to inducing anesthesia in order to saturate the patient""s blood with oxygen so as to increase the safety of a subsequent ventilation and endotracheal intubation. Pre-oxygenation of the patient is carried out by using a parallel oxygen supply and breathing system connected by means of a conduit to the anesthesia face mask affixed to the patient. Due to the complexity of such a technique, pre-oxygenation is often skipped.
In the case where pre-oxygenation is effected, while the patient is being pre-oxygenated, the doctor usually closes with his fingers the distal end of the conduit connected to an anesthesia machine and adapted to deliver an oxygen/anesthesia gas mixture to the patient, during operation of the anesthesia machine, so as to permit the anesthesia gas in the mixture to reach a preset concentration sufficient to induce anesthesia of the patient with a single breath. Since it is impossible to close with one""s fingers the anesthesia gas conduit in a gas-tight manner, leaks of anesthesia gas often occur, which pollute the operating room. When the desired concentration of anesthesia gas has been reached, the oxygen conduit is disconnected from the anesthesia face mask and the anesthesia gas conduit connected thereto. During this disconnection and connection of conduits, important leaks of anesthesia gas occur, which not only further pollute the operating room but lower the concentration of anesthesia gas in the oxygen/anesthesia gas mixture delivered to the patient so that single breath induction anesthesia of the patient is considerably slowed down.
It is therefore an object of the present invention to overcome the above drawbacks and to provide a single breath induction anesthesia apparatus which readily permits pre-oxygenation of the patient and single breath induction anesthesia thereof, without causing pollution of an operating room with anesthesia gas.
In accordance with the invention, there is thus provided a single breath induction anesthesia apparatus for anesthetizing a patient comprising: a gas delivery system for delivering at least one gas to said patient from a valve, said valve alternately providing selective gas flow communication between said gas delivery system and one of a first and a second gas flow circuit connected thereto, said first and second gas flow circuits each enabling independent gas flow therethrough; said first gas flow circuit comprising an oxygen supply system for providing oxygen to said patient, said oxygen supply system having a first oxygen inlet connected to a first oxygen source; said second gas flow circuit comprising an oxygen/anesthesia gas supply system for mixing oxygen, independently fed thereto from a second oxygen source without interrupting oxygen flow provided by said oxygen supply system from said first oxygen source to said patient, and at least one anesthesia gas at a preset optimum ratio to provide an oxygen/anesthesia gas mixture, said oxygen/anesthesia gas supply system permitting continuous circulatory flow of said oxygen/anesthesia gas mixture while oxygen from said second oxygen source and said anesthesia gas are additionally supplied thereto to ensure circulation of said oxygen/anesthesia gas mixture at said preset optimum ratio within said oxygen/anesthesia gas supply system sufficient to, when released to said gas delivery system, induce anesthesia of said patient with a single breath; and said valve including a single, flow diverting valve member movable between a first position and a second position, said first position providing gas flow communication between said oxygen supply system and said gas delivery system to deliver oxygen from said first oxygen source to said patient, thereby permitting pre-oxygenation thereof while simultaneously inhibiting gas flow communication between said oxygen/anesthesia gas supply system and said gas delivery system, and said second position providing gas flow communication between said oxygen/anesthesia gas mixture at said preset optimum ratio to said patient, thereby permitting single breath induction anesthesia of said patient while inhibiting gas flow communication between said oxygen supply system and said gas delivery system.
According to a preferred embodiment, the valve comprises a valve body having a first port in gas flow communication with the oxygen supply system, a second port in gas flow communication with the oxygen/anesthesia gas supply system and a third port in gas flow communication with the gas delivery system, and a valve member within the valve body. The valve member is movable between a first position whereat the first port is in gas flow communication with the third port and the second port is closed, and a second position whereat the first port is closed and the second port is in gas flow communication with the third port. Preferably, the valve body has first, second and third tubular branches, the first, second and third ports being defined at respective proximal ends of the first, second and third tubular branches, respectively.
According to another preferred embodiment, the second and third ports are disposed along a first axis and the first port is disposed along a second axis extending transversely of the first axis. The valve body has a generally T-shaped configuration with the second and third tubular branches extending along the first axis and the first tubular branch extending along the second axis. In such an embodiment, the valve member preferably has a T-shaped gas passage formed therein.
According to a further preferred embodiment, the valve includes stop means for arresting the movement of the valve member at each of the first and second positions. Preferably, the stop means each comprise cooperating abutment means disposed on the valve member and the valve body.
According to yet another preferred embodiment, the first tubular branch is provided with oxygen vent means for venting excess oxygen when the valve member is in the second position. Preferably, the oxygen vent means comprise an oxygen vent orifice formed in the wall of the first tubular branch and a removable closure member for selectively closing the oxygen vent orifice when the valve member is in the first position or opening the oxygen vent orifice when the valve member is in the second position.
Due to the provision of the aforesaid valve enabling selective gas flow communication between the oxygen supply system and the gas delivery system or between the oxygen/anesthesia gas supply system and the gas delivery system, the apparatus according to the invention permits pre-oxygenation of a patient and single breath induction anesthesia thereof, without causing pollution of the operating room with anesthesia gas.